The present invention relates to a continuously variable transmission, at times referred to as a CVT. Transmissions of this type are well known in the art, and comprise a pair of cone pulleys, each comprising a pair of sheaves or flanges, the pulleys being drivingly interconnected by a belt or the like. In the usual CVT, one pulley is connected to a drive shaft. At least one flange of each pulley is axially movable, with respect to the other flange, on its respective shaft. By varying the spacing between each pair of flanges of each pulley, continuous adjustment of the drive ratio can be provided between the shafts within the limits of pulley sizes. Means are usually provided for initiating the drive ratio changes and the prior art is replete with techniques of such means.
The axially movable flange of each pulley or a hub of such flange may be, according to the prior art, each provided with an internal keyway to receive a key received in a keyway in the respective shaft, thus providing the driving connection between flange and shaft while permitting the axial movement of the flange. Lubricating the key-keyway connection is difficult at times. Thus the key binds in the keyways and the movable flange behaves as a fixed flange, so that drive ratio changes are impeded. Loading on the key, under these circumstances, becomes excessive because of the physical mass of the pulley rotating at relatively high speeds, leading to premature failure of the transmission.
Another form of movable flange-shaft connection is the ball-spline in which a plurality of balls are used with a spline, the balls functioning as anti-friction elements. The ball-spline connection is located internally of the flange and/or its hub. Ball-spline connections are expensive and also require continual lubrication to insure continued performance. Loading on the spline of the ball-spline connection can also become excessive, leading to premature failure of the connection.